1. Field of the Invention
The present invention relates to an information reproducing system and an information reproducing method for obtaining a reproduced image of an n-times speed from a recording medium in which data encoded from video signals are recorded.
2. Description of the Related Art
Here will be described the actions of a magnetic recording/reproducing system of the prior art by taking the VTR (Video Tape Recorder) of the digitally recordable D-VHS (Registered Trademark) as an example. FIG. 13 is a block diagram showing a construction of the VTR of the prior art.
In FIG. 13, numeral 1 designates a drum; numeral 2 a pair of heads mounted on the drum 1 diametrically oppositely to each other at 180 degrees to have inverse azimuths; numeral 3 a capstan motor for running a tape; numerals 4 and 5 switches; numeral 6 a magnetic tape; numeral 7 a control (hereinafter abbreviated to “CTL”) head for recording/reproducing a CTL signal; numeral 8 a CTL reproduction amplifier; numeral 9 a phase control circuit; numeral 10 a speed control circuit; numeral 11 a reproduce amplifier; numeral 11 a reproduce amplifier; and numeral 12 a decoder; numeral 13 a CTL record amplifier; numeral 14 a record amplifier; numeral 15 an encoder; numeral 16 a monitor; and numeral 17 an FG (Frequency Generator) unit for outputting a signal of a period synchronized with the rotational period of the capstan motor 3.
At a recording time, the video signal, as inputted to the encoder 15, is encoded into digital data and sent to the record amplifier 14. At this time, the switch 4 is changed to the side of the record amplifier 14. The encoded video data, as outputted from the record amplifier 14, are recorded through the head 2 in the magnetic tape wound to run on the drum 1. The drum 1 is rotated in synchronism with the digital data to be recorded, and the capstan motor 3 is so controlled by the speed control circuit 10 and the phase control circuit 9 as to keep the period of the output of the FG unit 17 constant. At this time, on the other hand, the switch 5 is already changed to the side of the CTL record amplifier 13, from which the CTL signal synchronized with the video data is recorded through the CTL head 7 in the tape lower end.
FIG. 14 is an explanatory view of a track format to be recorded on the magnetic tape 2. In the tape lower end, there is recorded the CTL signal which is used at the reproduction time in the phase control of the capstan motor 3 for holding the tracking. In the recording track of the video data, there are buried in advance the video data for the n-times speed, the position of which is scanned by the head 2 to produce a reproduced image for the n-times speed reproduction.
At the reproduction, the output (FG signal) from the FG unit 17 is so controlled by the speed control circuit 10 that its period may be kept constant. At this time, on the other hand, the switch 5 is already changed to the side of the CTL reproduce amplifier 8 so that the reproduced output (CTL signal) from the CTL head 7 is inputted to the phase control circuit 9.
On the other hand, a PG signal of one pulse is inputted for one rotation of the drum from a PG unit 18 to a drum FF circuit 19. On the basis of the PG signal, the drum FF circuit 19 outputs a DFF signal indicating the rotational phase of the drum 1 and the timing for the head change, to the phase control circuit 9.
Where the output of the FG unit 17 is outside of a predetermined range, a fixed value is outputted from the phase control circuit 9 so that no phase control is made. Within the predetermined range, the control is made to keep a predetermined phase relation between the DFF signal indicating the rotational phase of the drum 1 and the CTL signal thereby to establish the tracking at the reproduction for the head 2 to scan the track. At this time, the switch 4 is changed to the side of the reproduce amplifier 11 so that the reproduced output from the head 2 is amplified and is sent as the video data to the decoder 12. In this decoder 12, the video data are decoded into a reproduced image, which is outputted to and displayed in the monitor 16.
Here will be described the n-times speed reproduction. At the video signal recording time, the data for the n-times speed reproduction are recorded together with the data for the ordinary reproduction in a predetermined track. At the n-times speed reproduction, the rotating speed of the capstan motor 3 is increased to n-times. If the FG signal and the CTL signal are divided into n-frequencies, however, the tracking can be stabilized as at the one-time speed reproduction by keeping the divided CTL signal and the rotational phase of the drum 1 constant. Since the CTL signal of n pulses is reproduced for one rotation of the drum 1, however, n-ways can be conceived on the tracking convergence positions of the head 2 and the track. Even if the tracking is stabilized, therefore, the n-times speed data are not sometimes be reproduced. Where the n-times speed data are not reproduced, the tracking position has to be changed by changing the phase target owned by the phase control circuit 9, by two tracks (or one CTL signal).